As a conventional technology for utilizing a swirl flow to facilitate the atomization of fuel injected from multiple fuel injection holes, the fuel injection valve described in Patent Document 1 (JP-A-2003-336562) is known.
In this fuel injection valve, a lateral passage and a swirl chamber are formed between a valve seat member and an injector plate. At the front end face of the valve seat member, the downstream end of a valve seat cooperating with a valve body is open and the injector plate is joined to the front end face of the valve seat member. The lateral passage communicates with the downstream end of the valve seat and the downstream end of the lateral passage is open in the tangential direction of the swirl chamber. A fuel injection hole for injecting fuel given a swirl in the swirl chamber is formed in the injector plate. The fuel injection hole is placed so that it is offset a predetermined distance from the center of the swirl chamber to the upstream end side of the lateral passage.
In this fuel injection valve, the curvature radius of the inner circumferential surface of the swirl chamber is reduced from the upstream side to the downstream side in the direction along the inner circumferential surface of the swirl chamber. That is, the curvature is increased from the upstream side to the downstream side in the direction along the inner circumferential surface of the swirl chamber. In addition, the inner circumferential surface of the swirl chamber is formed along an involute curve having its base circle on the swirl chamber. As a result, the facilitation of the atomization of fuel and the enhancement of injection response are achieved.
The fuel injection valve described in Patent Document 2 (JP-A-2008-280981) includes an orifice plate having: multiple perfectly circular swirling chambers (swirl chambers) for swirling fuel; fuel injection holes for injecting fuel; and fuel inflow passages for guiding fuel into the swirling chambers. The offset of each fuel injection hole from the central axis of a fuel inflow passage is made larger than the width of the fuel inflow passage and a curved spray group is thereby formed. Thus HC of exhaust gas is reduced by reducing fuel sticking to a wall surface. Further, soot is reduced to achieve the enhancement of the power of an internal combustion engine by injecting fuel with high dispersion.
One of products similar to the shape of the swirling chamber in the orifice plate of a fuel injection valve is the scroll of a centrifugal blower (compressor) as is found in Non-patent Document 1 (“Turbofan and Compressor,” Takefumi Namai). As one of basic design methods for centrifugal blowers, its shape is prescribed so that the flow rate is conserved at each section of the scroll. This makes it possible to define such a shape of the scroll that pressure loss is reduced and even turning is accomplished.